1. Field of the Invention
The invention relates in general to a wafer laser-marking method and a die manufactured using the same, and more particularly to a laser-marking method capable of precisely marking a desired pattern and a die manufactured using the same.
2. Description of the Related Art
Along with the rapid advance in technology, many electronic products featured by high speed, light weight, slimness and compactness are provided one by one. The main function of the packaging industry is to support the development of electronic products and assure that the speed of semiconductor packages keeps improving and the semiconductor packages function properly. Thus, the electronic products using the semiconductor packages can meet the market requirements of lightweight, slimness and compactness. In order to meet the users' needs, the way of packaging semiconductor packages also keeps being renewed so that the packages become further miniaturized.
Of the many factors that affect the development of the super-thinned package, the thickness of the chip is very crucial. The smaller the chip is, the easier it is to integrate many chips having different functions into one single small-sized package. The step of thinning the wafer is an indispensible step in the making of a small-sized chip. However, the thinner the wafer is, the easier the warpage will occur and affect subsequent process. For example, the laser light cannot precisely mark a pattern on the back surface of the wafer.
Referring to FIG. 1A˜FIG. 1D illustrate a conventional wafer laser-marking method. Firstly, a wafer 10 having a first surface (an active surface) 101 and a second surface (a wafer back surface) 103 is provided, wherein a plurality of bumps 12 are disposed on the first surface 101. Typically, the first surface 101 is the active surface (the circuit surface) of the wafer 10, and the second surface 103 is the back surface (the non-circuit surface) of the wafer 10. Next, an adhesive layer 14 is disposed on the first surface 101 of the wafer 10 as indicated in FIG. 1A. The adhesive layer 14 can be any back grinding (BG) tape applicable to the thinned wafer 10. Then, the grinding step is performed to thin the wafer 10 by grinding the second surface 103 of the wafer 10 as indicated in FIG. 1B.
After that, the periphery of the wafer 10 is fixed by a frame 16, then the wafer 10 and the frame 16 are positioned on a supporting structure (not illustrated), and a laser light is radiated on the second surface 103 of the wafer 10 to carve a desired laser marking (pattern), as indicated in FIG. 1C. The generated laser markings could be divided as large marks and white marks. Normally, a depth of large mark is approximately 0.1 μm, and a depth of white mark approximately ranges between 2 μm to 4 μm. Finally, the wafer 10 is singulated to form a plurality of dies 18.
However, as both the frame 16 and the supporting structure are both made of hard materials, warpage might easily occur to the thin wafer due to the gravity. That is, the center of thinned wafer 10 sinks and becomes lower than the two sides. It is very difficult for the laser light to precisely focus on the back surface of the wafer whose periphery has severe problem of warpage. The allowable tolerance of focusing point of the laser light (variation from a standard) is usually about 1 mm. Referring to FIG. 2, a wafer warpage and laser lights are schematically shown. As indicated in FIG. 2, the laser lights L1, L2, L3, L4 can be radiated on the back surface of the wafer to mark a pattern, wherein the laser light L1 corresponds to the center of the wafer. However, for the areas having server warpage (for example, the periphery of the wafer), the focal point of the laser light is not able to reach the back surface of the wafer. Take the laser light Ln for example, there is a distance between the focal point a of the laser light Ln and the back surface of the wafer, the laser light therefore cannot be radiated on the back surface of the wafer to mark a pattern precisely. Thus, the marking on the wafer has defects, not only reducing product yield rate but also increasing manufacturing cost.